Adult sea lice attach to salmon by hooking on the scales of the fish, by attaching a filament, or by suction. Sea lice develop through several life stages. The most concerning stage is adult and sub adult stages wherein sea lice are mobile and seeking attachment. Once attached, the sea lice are capable of surviving forward motion of the fish. As fish naturally swim upstream against a current, the sea lice are positioned to remain attached to the fish.
A velocity differential between the fish and water can be used to remove sea lice. In this manner, sea lice are readily removed when the water velocity is reversed, namely flowing from the tail of the fish toward the head of the fish.
In some locations, government regulations require minimum sea lice concentrations. If sea lice concentrations are too high, fish stocks must be harvested immediately. The result is a monetary loss to the farmer due to the lower value of small fish and higher per kilogram cost.
The minimum sea lice removal from fish stock, to control sea lice concentrations, must be over 90% or repopulation of the sea lice rapidly occurs. The removal of the sea lice must also reduce or eliminate damage to the fish.
Fish pumps used to transfer fish commonly use a suction which causes the fish to enter the fish pump tail first. Since the natural tendency of a fish is to move against a current, the fish enter a fish pump swimming away from the suction flow, thereby entering an intake line tail first. Fish that enter a fish pump, or other current producing device, receive a predictable velocity gradient from head to tail and the hooked on lice stay hooked. Test results indicate that for salmon entering water streams of 0.3 to 1 ft/sec from head to tail reflect almost no sea lice removal.
Spinning and turbulence is a problem when pumping live fish. When the fish is pumped for sea lice removal, the fish must be returned for continued growth after processing. Minimizing injury to the fish is critical to avoid bleeding gills or lost slime and scale which commonly result in fish mortalities.
Coanda effect pumps are known for their beneficial use in pumping fish. A problem for known Coandas effect pumps is that the flutes are very shallow or no flutes exist. Also the designs inherently have a high pressure at the primary water entrance impacting the inner tube and opposite 180 where the high velocity water meets and velocity becomes pressure.
Another problem with conventional Coanda pumps is the sudden turbulence or swirl due to the differential energy in the circumferential primary flow and the inner column of induced flow. Large active fish can be severely injured at this junction, wherein scales and fins can be torn off or side wall impact so severe that the fish can be killed.
Spinning or undesirable water velocities cause the fish to struggle in the flow pipes and often damage themselves loosing scales and slime that protect them from disease. The current invention solves both of these problems with larger flutes and changing depths to stop spinning and balance or alter pressure distribution for ideal water flow to eliminate fish damage.
Patents relevant to this industry include Coanda, U.S. Pat. No. 2,052,869, which describes the original pump, now referred to as the Coanda effect pump.
Baker, U.S. Pat. No. 3,655,298, includes circumference water injection at an angle, but does not use a cone or Coanda effect.
Mays, U.S. Pat. No. 3,664,768, discloses a jet pump improved with succession of radially inwardly stepped wall segments, numbers 380, 80, of said tubular housing.
Mocarski, U.S. Pat. No. 3,795,367, discloses a Coanda effect device that mixes the primary and secondary flow with discharge flow.
Hillis, U.S. Pat. No. 4,155,682, discloses a pump including an upstream and downstream high pressure nozzle with different inclined angles of entry in a jet pump to improve efficiency by reducing turbulence and boundary layer.
Westfall, U.S. Pat. No. 4,702,676, discloses a pump with multiple nozzles similar to the Hillis U.S. Pat. No. 4,155,682, with claim 2 including pressurized gas.
Nagata, U.S. Pat. No. 4,487,553, discloses a series of circumferentially spaced nozzles. This disclosure does not use a Coanda effect pump to reduce the turbulence and cavitation required for moving fish without damage.
Halse, U.S. Patent Publication No. US2017/0325432, discloses a pumping system that includes a vacuum pump, valves and buffer pipe to recycle water while pumping fish.
Breckner, U.S. Pat. No. 5,018,946, discloses an early Coanda effect pump. The Coanda effect is the property of a fluid to follow a curved surface, see. Breckner, which describes a pump using uniform surface in the Coanda surfaces.
Lillerud, WO 2014/184766, discloses an improvement of sea lice cleaning with gas bubbles.
Hansen, WO 2016/189146, comprises a cylinder with holes and water injection at both ends to scrape sea lice from fish. It is not a pump with Coanda effect.
There are various ways to get fish entered head first, including the system set forth by Lindgren in Patent Publication application U.S. 2018/0206458) and the use of special pumps, as in Lemmon, U.S. Pat. No. 4,193,737.
Lindgren, U.S. Pat. No. 7,462,016, discloses an improved fish lift for processing larger fish on larger boats. Lindgren is a modified Coanda effect pump to improve lift. This patent was designed to improve the capacity of the early Coanda effect fish pump, and included flutes in the interior water injection flow path to more efficiently effect the far field of water flow, and therefore, improves lift and flow capacity. The Lindgren pump, marketed under the mark SILKSTREAM™, passes approximately 21% of the flow through the flutes. It has been found that the Lindgren pump will remove up to 70% of sea lice (Lepeophtheirus salmonis) from salmon.
In particular, the SILKSTREAM™ pump enters water through a tube concentrically at a high velocity on a curved cone surface to create inlet suction. For example, a 10 inch pump commonly used on salmon fish requires approximately 2,000 GPM for a 2 meter lift. The inlet water with fish will be approximately 1,500 GPM. The water stream tube surface will triple velocity in less than 4 inches. The SILKSTREAM™ pump has been found to be exceptionally beneficial in the removal of sea lice when the fish is drawn through the pump head first.
What is needed in the art is an improved pump that is directed to increasing the removal of sea lice, while reducing or eliminating damage to fish during transfer. The improved pump is focused on fish welfare, and can process the fish fast, effectively, and efficiently with minimal stress.